DNS 2 SERVFAIL vs 22 BADTRUNC
Both DNS 2 (SERVFAIL) and 22 (BADTRUNC) belong to the DNS Response Codes (RCODEs) category. 2 indicates that server failure. The name server encountered an internal error while processing the query. Meanwhile, 22 means that bad truncation. The TSIG record was truncated in a way that makes it impossible to verify the message signature.
Description
Server failure. The name server encountered an internal error while processing the query.
When You See It
The recursive resolver could not get an authoritative answer — commonly caused by DNSSEC validation failures, unreachable upstream nameservers, or misconfigured zones.
How to Fix
Try a different resolver (e.g., 8.8.8.8 or 1.1.1.1) to isolate the issue. If you control the zone, check DNSSEC signatures, SOA serial consistency, and nameserver reachability.
Description
Bad truncation. The TSIG record was truncated in a way that makes it impossible to verify the message signature.
When You See It
A large DNS response was truncated (TC bit set) but the TSIG MAC was computed over the full message, making the truncated version unverifiable.
How to Fix
Retry the query over TCP to avoid truncation. If using UDP, ensure your EDNS buffer size is large enough to receive the full signed response.
Key Differences
DNS 2: Server failure. The name server encountered an internal error while processing the query.
DNS 22: Bad truncation. The TSIG record was truncated in a way that makes it impossible to verify the message signature.
You encounter 2 when the recursive resolver could not get an authoritative answer — commonly caused by DNSSEC validation failures, unreachable upstream nameservers, or misconfigured zones.
You encounter 22 when a large DNS response was truncated (TC bit set) but the TSIG MAC was computed over the full message, making the truncated version unverifiable.
When to Use Which
For 2 (SERVFAIL): Try a different resolver (e.g., 8.8.8.8 or 1.1.1.1) to isolate the issue. If you control the zone, check DNSSEC signatures, SOA serial consistency, and nameserver reachability. For 22 (BADTRUNC): Retry the query over TCP to avoid truncation. If using UDP, ensure your EDNS buffer size is large enough to receive the full signed response.